Name: group7a Exercise 9: Renal System Physiology: Activity 6: The Effect of Hormones on Urine Formation Lab Report Pre-lab Quiz Results You have not completed the Pre-lab Quiz.
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Experiment Results Predict Question: Predict Question 1: What will happen to the urine volume (compared with baseline) when aldosterone is added to the distal tubule? Your answer : b. The urine volume will decrease. Predict Question 2: What will happen to the urine volume (compared with baseline) when ADH is added to the collecting duct? Your answer : a. The urine volume will increase. Predict Question 3: What will happen to the urine volume and the urine concentration (compared with baseline) in the presence of both aldosterone and ADH? Your answer : b. The urine volume will decrease and the urine concentration will increase. Stop & Think Questions: Why is the concentration in the urinary bladder 100 mOsm? You correctly answered: c. No ADH has been added to this nephron. In the presence of aldosterone, what component of the tubule fluid moves out of the distal tubule and into the interstitial space? You correctly answered: a. NaCl In the presence of ADH, why did the urinary potassium concentration increase? You correctly answered: c. The water volume in the urinary bladder is decreased, increasing the concentration of solutes such as potassium. In the presence of both ADH and aldosterone, why did the urinary potassium concentration increase? You correctly answered: c. There was more potassium secretion into the distal tubule and more water reabsorption in the collecting duct. Experiment Data: Potassium Conc. in Urine 6.25 10.42 62.37 65.37
Urine Volume
Urine Conc
Conc. Grad.
Aldosterone
ADH
201.00 180.90 16.86 12.67
100 100 1200 1200
1200 1200 1200 1200
absent present absent present
absent absent present present
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Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. If there has been a significant loss of fluid from the body, the kidneys will generate __________ urine. You correctly answered: d. hyperosmotic 2. If you drink a large volume of water, the kidneys will generate __________ urine. You correctly answered: b. hypo-osmotic 3. In response to dehydration, ADH will be released from the You correctly answered: c. posterior pituitary gland. 4. In response to abnormally low plasma osmolality, aldosterone will increase You correctly answered: a. sodium reabsorption along the distal tubule and the collecting duct.
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Review Sheet Results 1. How did the addition of aldosterone affect urine volume (compared with baseline)? Can the reabsorption of solutes influence water reabsorption in the nephron? Explain. How well did the results compare with your prediction? Your answer: Aldosterone acts to increase the production of 3 types of channels: 1) sodium channels 2) potassium channels 3)sodium potassium pump (Na+/K+ATPase) These 3 channels promote the reabsorption of sodium into the cell which in turn, pulls water with it into the cell. Potassium leaves the cell at the same rate sodium enters so it balances the cell. but sodium attracts water into the cell and potassium has no effect on water movement. When sodium is reabsorped into the bloodstream so is the water, which overall again acts to reabsorb water from the urine, concentrating it, and increasing the amount of water in the blood. The results coincided with our prediction. 2. How did the addition of ADH affect urine volume (compared with baseline)? How well did the results compare with your prediction? Why did the addition of ADH also affect the concentration of potassium in urine (compared with baseline)? Your answer: ADH acts on the cells of the collecting ducts of the nephron in the kidney. ADH diffuses out of the blood stream and binds to its receptor found on the basolateral membrane of the collecting duct cell (this is the side of the cell that faces the blood). When it binds to its receptor it causes an intracellular casade (a reaction within the cell) that has the result of: 1) increasing the production of aquaporins in the cell. these aquaporins travel to the apical membrane of the collecting duct where they are inserted into the apical membrane. 2) Cause vesicles that contain aquaporin channels, that are already present in the cell (like a reserve of these channels), to fuse with the apical membrane and thus inserting those aquaporins into the membrane. The apical membrane is the side of the cell that is facing the lumen of the nephron (where the urine is). Aquaporins are channels that allow water to flow through them very fast and easily. With more aquaporins in the membrane, more water can flow into the cell. there is more water in the lumen of nephron than in the cell and so water flows down its osmotic gradient into the cell and then out the opposite side (basolateral membrane) and into the blood. The results coincided with our prediction. ADH secretion also causes potassium secretion into the lumen of distal convoluted tubules. 3. What is the principal determinant for the release of aldosterone from the adrenal cortex? Your answer: 1. blood volume: when there is a volume loss, this will trigger renin- angiotensin system which will cause the secretion of aldosterone hormone (via angiotensin II) to force the kidneys to absorb more Na and hence more water. 2. plasma potassium concentration: any rise in the potassium level will trigger aldosterone release (which will cause more
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potasuim to be lost with urine). 4. How did the addition of both aldosterone and ADH affect urine volume (compared with baseline)? How well did the results compare with your prediction? You did not answer this question. 5. What is the principal determinant for the release of ADH from the posterior pituitary gland? Does ADH favor the formation of dilute or concentrated urine? Explain why. You did not answer this question. 6. Which hormone (aldosterone or ADH) has the greater effect on urine volume? Why? You did not answer this question. 7. If ADH is not available, can the urine concentration still vary? Explain your answer. You did not answer this question. 8. Consider this situation: you want to reabsorb sodium ions but you do not want to increase the volume of the blood by reabsorbing large amounts of water from the filtrate. Assuming that aldosterone and ADH are both present, how would you adjust the hormones to accomplish the task? You did not answer this question.
